Manufacture of amorphous-silicon thin film transistors-liquid crystal displays (TFT-LCD) usually employs back channel etch technique.
As shown in FIG. 1, a method for manufacturing the thin film transistors includes: forming a gate layer pattern including a gate electrode 2 on a substrate 1, forming a gate insulating layer 3, forming successively an active layer 4, a source-drain electrode layer 5 and a photoresist layer 6 on the gate insulating layer 3; wherein the active layer can include a semiconductor layer 41 and an ohmic contact layer (a doped semiconductor layer) 42 (as shown in FIG. 1).
The substrate coated with the photoresist layer 6 is exposed and developed by using a gray-tone or half-tone mask to form an unexposed region 61 of the photoresist, a partially exposed region 62 of the photoresist and a completely exposed region 63 of the photoresist, as shown in FIG. 2. A first etching process is performed, the source-drain electrode layer and the active layer in the completely exposed region of the photoresist are etched since there is no photoresist to protect them, as shown in FIG. 3. An ashing process is performed, the photoresist remained on the partially exposed region 62 of the photoresist is removed, the photoresist remained on the unexposed region 61 of the photoresist is thinned, as shown in FIG. 4. A second etching process is performed, the source-drain electrode layer in the partially exposed region of the photoresist is etched firstly, so as to form a source electrode 51 and a drain electrode 52; then a part of active layer 4 between the source electrode 51 and the drain electrode 52 is etched, and the doped semiconductor layer 42 in the active layer is completely etched, as shown in FIG. 5; finally, the photoresist is peeled off, as shown in FIG. 6.